How to detect if all json element was used to create Java Object

Question

I want to apply "stern" strategy on my rest api endpoint (https://stackoverflow.com/a/20597044/4828427). As parameter i am not using JsonObject but MyObject.

@RequestMapping(value = "/api/v1/authenticate", method = RequestMethod.POST)
    public ResponseEntity<TokenDTO> createAuthenticationToken(@RequestBody JwtRequest authenticationRequest) {

So i let spring deserializate json to object and i am using object dirrectly. Example:

authenticationRequest.getUsername();

I am looking for some Utils or annotations to detect if there are any unused json elements in request or not to handle it with proper warning handler.

As an option you can define your custom `ObjectMapper` as a `Bean` and make it fail when `unknown` or `missing` properties are encountered in your json. `new ObjectMapper().configure(DeserializationFeature.FAIL_ON_MISSING_CREATOR_PROPERTIES, Boolean.TRUE).configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, Boolean.TRUE);` — Serg Vasylchak, Sep 06 '19 at 12:48
Could you clarify what do you expect to get as an output of that validation? A 400 status code? Just log a WARN statement? — pca, Sep 06 '19 at 13:05

score 0 · Accepted Answer · answered Sep 06 '19 at 19:38

You can use @JsonAnySetter like this:

1- you define a BaseRequestDTO class:

public abstract class BaseRequestDTO {
    @JsonAnySetter
    public Map<String, Object> additionalData=new HashMap<>();
}

the field additionalData will hold all json field not in your DTO

2- make your dto extend it, like:

class JwtRequest extends BaseRequestDTO{
   public String  username;
   public string password;
}

3- write an aspect to apply your "stern" strategy:

@Aspect
@Component
public class ControllerArgsValidator {
    @Pointcut("within(@org.springframework.web.bind.annotation.RestController *)")
    public void restController() {
    }
    @Pointcut("within(@org.springframework.stereotype.Controller *)")
    public void controller() {
    }

    @Around("controller() || restController()")
    public Object validate(ProceedingJoinPoint point) throws Throwable {
        Object[] args = point.getArgs();
        for (Object arg : args) {
            if (arg instanceof BaseRequestDTO) {
                if((BaseRequestDTO) arg).additionalData.isEmpty())
                    //do what ever;
            }
        }
        return point.proceed();
    }

for me was enough to see @JsonAnySetter annotation, but still is good to know how to preprocess controller — alibaab, Sep 11 '19 at 08:05

How to detect if all json element was used to create Java Object

1 Answers1